P-51 Compression

[Spatula]

Am i just plain mad (thats rhetorical folks), or is there a 'magic' speed where all of a sudden the p51 controls just lock up totally? you can get out if ya got alt and use lots o trim and full rudder and no throttle (to try slow down). I dont contest the fact the plane should suffer from compression, far from it. It seems that there is a magic speed where it will suddenly change from controllable(ish) to locked, and when you slow down and pass that magic speed again it frees up. shouldnt this happen gradually (or at least progressively, even if it is fast)? It seems that it goes instantly from controllable to locked - like someone took off ya elev (and no they didnt).

Any other stang pilots noticed this? Seems to happen at just above 500 IAS.

Anyone????

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Overlord Spatula

if you adhere to all the rules you miss out on all the fun
 

=357th Pony Express=

[This message has been edited by Spatula (edited 07-04-2000).]

[airspro]

600 TAS or the "red" needle is the magic # .

I watch that speed like a hawk now  

I ain't much of a pilot here yet , but that's pretty damn fast .

You might try this   change the wind noise wav file to say overspeed . One of our members has that done , he took the file out of Falcon 4.0 .

You know how loud that wind gets at that speed so for him it's now a BIG noisy warning  

cheers  spro  

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air_rules = Play fair ....Don't worry about points......Keep a sense of humor......Drink Jim Beam......and don't let the fediddlein cat walk on the keyboard.......!!!http://www.airsquadron.com" TARGET=_blank>
             

[This message has been edited by airspro (edited 07-04-2000).]

[funked]

It's called critical Mach.  Deal with it.

[Spatula]

   

Originally posted by funked:
It's called critical Mach.  Deal with it.

Funked i am aware of what it is, and i am dealing with it. Read my post again.

   

Originally posted by Spatula:
I dont contest the fact the plane should suffer from compression, far from it.

My point was, and maybe it wasnt that clear: It just seems strange that (and i'll use airspros example of 600 TAS) at 599.99999 TAS it handles reasonably well, but as soon as you got that 0.00001 knots faster and hit 600 TAS it just suddenly changes to completely unresponsive. and as soon as you slow down past 600 TAS to 599.99999 TAS it goes back to reasonbly manueverable.


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Overlord Spatula

if you adhere to all the rules you miss out on all the fun
   

=357th Pony Express=


[This message has been edited by Spatula (edited 07-04-2000).]

[Zigrat]

Yup, its because a shock is forming. The shock forms when the air speed of the plane is great enough to cause the local velocity of the air over the wing to exceed mach 1. Then, behind the shock there is a large increase in pressure, decrease in airspeed, and a increase in temp. So when the shock is in front of a control surface, it loses effectiveness.

[Rocket]

Spat are you saying this comes on way too fast without any warning?

IE. couple of mph before the magic number things start to act a little strange gradually getting worse until total compression?

S!

Rocket

[funked]

I should have been more clear.

"It seems that there is a magic speed where it will suddenly change from controllable(ish) to locked,"

The magic speed is the critical Mach.  That's when compressibility effects start.

"It seems that it goes instantly from controllable to locked - like someone took off ya elev (and no they didnt)."

That's how some WWII pilots described it.  

[This message has been edited by funked (edited 07-04-2000).]

[chisel]

Liked your first answer better funked.

Made you sound like the grizzled old veteran you are.  

[Spatula]

 

Originally posted by Rocket:
Spat are you saying this comes on way too fast without any warning?

It comes on instantly, the only warning is your ASI and the creaks  

 

IE. couple of mph before the magic number things start to act a little strange gradually getting worse until total compression?

Nup, the controls stiffen as you'd expect as you approach 500 IAS and gradually get stiffer but at the magic speed it just instantly changes to locked up from controllable. Just seems strange.

Funked, thanks, i guess having never had it modelled before and not knowing exactly how it effects the controls, i didn't expect this sort of behaviour. I expected it to be a bit more gradual than the off/on switching that it seems to be. Also i havent noticed it in any other plane.

I will accept your explantion  

Cya up (and in the bish camp too)
 

[This message has been edited by Spatula (edited 07-05-2000).]